Recent advances may signal ‘landmark year’ for foodborne illness

Issue: June 2015

The detection and prevention of foodborne illnesses may not be new challenges to public health, but they certainly are lasting ones.

Since 1996, the CDC’s Foodborne Diseases Active Surveillance Network, or FoodNet, has guided national food safety policies by monitoring trends among commonly acquired illnesses. Despite new regulations and changes within the food industry during the past 19 years, reported incidents are still well above targets set by the Healthy People 2020 initiative.

Developments in the detection of foodborne illnesses and updated regulations from government agencies, however, we could signal a turning point in the near future, according to Rob Tauxe, MD, MPH, deputy director of the CDC’s Division of Foodborne, Waterborne and Environmental Diseases.

“This is a particularly interesting moment in foodborne illnesses … a landmark year,” Tauxe told Infectious Diseases in Children. “The report each year, for a number of years, has shown that we aren’t making much progress, but I think the next year could be the year it changes.”

Herbert L. DuPont

While a growing reliance on imported food has been challenging, Tauxe said new produce regulations coming from the FDA later this year will be a step forward for fruits and vegetables grown both domestically and abroad. Improved Salmonella and Campylobacter performance standards for meat and poultry, which recently were introduced by the Agriculture Department, should reduce the spread of these bacteria, while an FDA requirement that livestock be treated with antibiotics only upon receipt of a Veterinary Feed Directive will help address the development of antibiotic-resistant pathogens.

Improved diagnostics

Just as important as the prevention of new foodborne illnesses, however, is the detection of outbreaks, an area within the field that has ample room for improvement.

“The CDC says we have 48 million cases a year, but we have many, many more than that,” Herbert L. DuPont, MD, director of the Center for Infectious Diseases at the University of Texas School of Public Health and an Infectious Disease News Editorial Board member, said in an interview. “That estimate is probably low considering there are as many as 179 million cases of diarrhea every year in the United States.”

For nearly 2 decades, pulsed-field gel electrophoresis (PFGE) has been the standard diagnostic used by the CDC and public health laboratories. The decreasing cost of whole-genome sequencing, however, has led molecular epidemiology to combine the two methods for improved results. According to Tauxe, this has been a significant factor in the frequent detection of Listeria infection during the past year.

“Using this whole-genome sequence in public health looks like a very powerful tool,” Tauxe said. “We plan to move forward with broader application, to Escherichia coli O157, and then after that some serotypes of Salmonella. We anticipate that within 5 years, the whole public health system will have switched over to whole-genome sequencing … and we’ll be finding and controlling outbreaks faster and better than ever.”

In addition, the rise of rapid multi-analytic platforms has led many clinical labs to adopt these newer diagnostics. Capable of testing for several pathogens simultaneously within a single specimen, they offer clinicians the ability to more quickly treat a patient’s infection.

Unfortunately, these platforms come at the cost of effective epidemiology. Because the tests do not produce an isolate, genetic subtyping, antimicrobial susceptibility and other data are unavailable from these results.

“We certainly understand the appeal of having a rapid diagnosis rather than waiting overnight or longer for something to grow in an incubation system,” Tauxe said, “but all the questions an ID doctor … and public health want to ask can’t be answered at this point, unless we also get an isolate. That’s why it’s critical to culture the fecal specimen that is positive on a rapid test.”

According to FoodNet survey data recently published in MMWR, 46% of the 5,614 positive culture-independent diagnostic tests (CIDTs) reported by clinical labs from January 2012 to December 2013 were unconfirmed by culture-based testing. Only 22% of the 2,497 positive CIDTS for Campylobacter were culture-confirmed, while the incidence of Campylobacter per 100,000 population was 14.1 and 2.1 for culture-confirmed and nonconfirmed CIDTS, respectively.

“As more clinical laboratories adopt CIDTs, the collection and detailed characterization of bacterial isolates that support public health activities will fall more heavily on public health laboratories,” CDC researchers wrote. “The increased reliance on CIDTs will create a burden for public health laboratories and will have a significant impact on clinical practice, outbreak detection and the ability to monitor disease burden and trends."

Rob Tauxe

But despite this threat to outbreak tracking, novel analysis techniques do show promise. Developed through a collaboration between the FDA, CDC and the Agriculture Department, new methodology that uses food-related variables improved attribution estimates and, according to the collaboration’s researchers, could enhance each agency’s efforts to prevent foodborne illness.

Patient awareness and education

Regardless of these advancements, safe food preparation remains an important way to prevent foodborne infections. Both Tauxe and DuPont emphasized that public awareness of cross contamination, as well as proper practices when washing or cooking meat, poultry and produce, could go a long way toward preventing these illnesses.

Alongside hygiene advocation, DuPont said physicians and infectious disease specialists need to improve their awareness of complications of enteric infection, including the post-enteric infection complications.

“Irritable bowel syndrome involves up to 15% of the public, and one-third of those occurred after a bout of enteric infection and are called post-infectious IBS,” DuPont said. “Guillain-Barré syndrome, reactive arthritis and other complications after foodborne enteric infections are issues that might be preventable … if enteric infections can be reduced.”

Physicians also should be aware of patients at higher risk of foodborne illness, such as those who are very young, elderly, pregnant or immunocompromised. DuPont and Tauxe said that properly educating these patients, as well as those not at risk, plays a substantial role in fighting future outbreaks.

“There are a lot of different infections, like Salmonella, Campylobacter, Shiga toxin-producing E. coli, and norovirus, and we see these as preventable,” Tauxe said. “They’re preventable by taking more care with the way our food is prepared in the kitchen. They’re preventable by steps that can be taken back in the food chain. It’s an issue where there’s room for a lot of progress.” – by Dave Muoio

References:

CDC. Foodborne Diseases Active Surveillance Network (FoodNet). Accessed March 18, 2015 at: www.cdc.gov/foodnet/.
Iwamoto M, et al. MMWR. 2015;64:252-257.

For more information:

Herbert L. DuPont, MD, can be reached at hdupont@stlukeshealth.org.
Rob Tauxe, MD, MPH, can be reached at RVT1@cdc.gov.

Disclosure: DuPont and Tauxe report no relevant financial disclosures.